Using a room as a server room, there can be computing machines such as servers installed in the room. Providing the computing machines are servers, for instance, such the server room is referred to as a data center. Such computing machines dissipate heat while working. If installed servers increase in number, like the case of data center, the whole servers have increased heat dissipation, so there is use of an air conditioner for producing cold air, to supply to a data center, by blowing up from under the floor, for instance. Further, there are fans provided to servers, or for racks accommodating servers therein, and adapted to intake cold air for cooling servers. There are fluxes of air warmed by servers being cooled, and let out of servers, to discharge as return air from the data center. Flux of return air discharged from the data center may be cooled at the air conditioner, to again provide to the data center, or discharged outdoor, as evacuation of air.
For such an air conditioning of data center, there was a technique using a set of racks of a type that accommodated therein a server or servers and took in cold air at the front side to let out as return air through the upside or the back, and a set of roundabout preventing devices each preventing streams of return air from going roundabout toward the front side. For instance, this might be a set of shield plates fixed to upsides of racks to prevent return air from mixing with cold air, allowing for effective use of cold air.
Also, there was a technique using an air blowing fan improved for efficient cooling. It employed a fan tower (as an air blowing device) installed in a server room, and configured to have fluxes of air suctioned from lower spatial regions in the room, to blow out into upper spatial regions, so air was suctioned into upper portions of racks. In this configuration, the air blowing device served to send cold air in a lower space in the room to an upper space, so those fluxes of air being suctioned from the upper space had lower temperatures than ever. Further, racks had decreased fluxes of cold air in their lower portions, where temperatures were raised higher than ever, so as a whole, they had reduced temperature gradients in the vertical direction, with reduced variations in temperature of suctioned air. In addition, their bottoms had openings formed therethrough, with adjusters operable to open and close, affording to suppress variations in temperature of cold air, allowing for saved energy, as well.
However, those techniques in the past had fluxes of air delivered from fans to supply to racks, driven by fans at the racks to blow onto servers, cooling them, discharged as fluxes of return air from the racks, and suctioned by a return air fan at an air conditioner, without mixing with cold air. That is, there was a connected single-duct configuration having those air streams striking therethrough, though there being the air conditioner and servers as flow passage resistances. On the other hand, for the single-duct configuration, there was use of fans forcing air therethrough, with actions of the fans interfering with each other, not simply causing air streams to be unstable, but also consuming undue power, as an issue.
Further, for such fans, there was use of speed uncontrollable induction motors affording to have equilibrium flux converged in accordance with a balance of air flow between the fans. However, for fans put under an inverter revolution number control, there were revolution numbers insisted in between, with their situations of revolution number control interfering with each other, causing hunting, as another issue.